Signalling apparatus incorporating a differential relay



Dec. 7, 1965 P. GIUFFRIDA 3,222,662

SIGNALLING APPARATUS INCORPORATING A DIFFERENTIAL RELAY .Filed Dec. 27, 1961 United States Patent This invention relates to fire detection apparatus.

Numerous different types of apparatus have been proposed for performing fire detection functions which operate on a variety of principles. Among these are devices which employ heat sensing elements such as bimetallic members, flame sensing elements such as those sensitive to either infra red radiation or ultraviolet radiation, and

smoke detecting arrangements. Conventional fire detectors include a sensor that is responsive to a particular ef fect associated with smoke, temperature or flame. Both for reliability of fire detection and for greater versatility and less criticality in application, it is desirable that a fire detector be responsive to more than one particular fire condition. For example there are combustible materials which may give off large quantities of smoke without great increase in temperature, while the burning of other materials generates a substantial temperature increase without producing much smoke. Further, in many cases flame will be obscured, at least at early stages of the fire, from the sensor element. In such situations a single sensor type of detector must be carefully engineered for application in appropriate environments only and care must be taken in placing the detector in those environments to insure that the detector will respond to the type of fire that is likely to occur. Even then continued checks on the protected area should be maintained, so that the detection apparatus may be revised if the nature of fire producing materials located in the area is changed, for example. In many cases such continued checks .are unfeasible from an economic viewpoint and a more versatile fire detector i desirable.

' Accordingly, it is an object of this invention to provide a novel and improved fire detection apparatus incorporating a plurality of different fire condition sensor elements.

Another object of the invention is to provide a compact, reliable and relatively inexpensive fire detection unit responsive to both heat and smoke conditions.

Still another object of the invention is to provide in a fire detection apparatus reliable electrical circuitry incorporating checking circuitry providing a signal on the failure of the less reliable components of the circuitry.

In a preferred embodiment constructed in accordance with principles of the invention there. is provided a detector unit having a casing defining a passageway adapted to be substantially vertically disposed. The passageway includes a lower or entrance aperture adjacent which a heat sensor is mounted; an upper or exit aperture adjacent which an airflow inducing elements is mounted; and an intermediate restriction across which a particle (smoke) sensor is disposed for scanning air flowing through the passageway. Also mounted within the casing is electrical circuitry for operating the heat and particle sensors and a common alarm system that is responsive to both the heat sensor and the particle sensor, so that a compact fire and smoke detector unit which generates an output signal in response to a plurality of different fire characteristics is provided. The output signal may operate an alarm or associated equipment as desired.

In the preferred embodiment of the invention the heat sensor includes a completely exposed, compensated bicell arrangement which senses light reflected from par- "ice ticles in the air flowing through the unit. Electrically the particle sensor includes a cadmium selenide photocell that is connected in circuit with the bimetallic element so that a signal from either of these devices is applied to the control grid of a cold cathode thyratron arranged to energize one coil of a two coil differential relay to provide an output signal. The one coil is in the anode circuit of the thyratron and the second coil of the relay is connected in series circuit with the particle sensor light source and the heater (air flow inducing) element so that if either fails the second relay coil is deenergized and a warning signal is generated. Reset means, connected in the thyratron anode circuit enable the circuit to be reset after operation in response to the particle or heat sensors but prevents resetting if the component elements are defective.

The invention provides a comparatively inexpensive and reliable fire detector apparatus in a compact assembly of sensor elements responsive to a plurality of fire indicating conditions. The apparatus provides an output signal in response to the detection of an abnormal condition indicative of a fire and also signals failure of components within the apparatus. It is a compact apparatus that has versatility in application and does not require extensive scheduled maintenance.

Other objects, features and advantages of the invention will be seen as the following description. of a preferred embodiment thereof progresses in conjunction with the drawing, in which:

FIG. 1 is a perspective view, partially in section and partially diagrammatic, of a fire detecting unit constructed in accordance with the principles of the invention;

FIG. 2 is an elevational view illustrating certain features of the heat sensor unit employed in the preferred embodiment of the invention; and

FIG. 3 is a schematic diagram of the electric circuit employed in the fire detector unit illustrated in FIG. 1.

With reference to FIG. 1, the fire detector unit includes an enclosure or casing 10 which houses the senor elements, associated electrical circuitry and alarm device. The casing has a cover 11 which can be easily removed for access to components within. The casing, which is adapted to be disposed in substantially vertical position, has a lower entrance aperture 12 and an upper exit aperture 14 above which is disposed a chimney-like structure 16. A passageway through the casing connects the entrance and exit apertures. Disposed immediately inside the casing above the entrance aperture is a heat sensor 18 and disposed in the chimney 16 is a heat producing unit in the form of an electrical resistance element 20. This element 20 tends to produce a flow of air through the casing passageway from the entrance aperture to the exit aperture by thermal convection.

At an intermediate point in the chamber 22 formed by the passageway there is a restricted area formed by protruding members 24 which extend from the casing walls and define a relatively narrow gap 26 through which the air flowing through the passageway must pass. Across this gap aparticle sensor is disposed. Formed in one of the protrusions on one side of the gap 26 is a cylindrical depression 28 with its interior surface coated with black material or otherwise rendered suitably non-refleeting.

In the other protrusion on the opposite side of the gap is -a cadmuim selenide photocell 30 and associated optics 32 disposed to scan across the gap towards the nonreflecting well 28. A light source 34 mounted within the lower portion of the casing has its focused light beam aimed to pass through the gap 26 substantially normal to the scanning direction of the photocell. As indicated in FIG. 1 the radiation from the source 34 is beamed in a are equal and opposite and hence cancel.

slightly diagonal direction across the chamber but substantially parallel to the path of air flow through the chamber so that light reflected by particles in the air flowing past the gap will be sensed by photocell 30. Power for the unit is supplied over lines 36 from a suitable household 110 volt source, for example.

The heat sensor element 18, as shown in FIGS. 1 and 2, comprises two bimetallic elements 40, 42 that are completely exposed to air flow and hence will rapidly respond to temperature changes in the supervised environment. 10

The sensor is mounted directly below the photocell housing 24. The bimetallic element 40 has a larger mass but is shorter than element 42, being approximately 75% of the length of that element. The two elements are secured by suitable means such as rivets 44 to a block 46 mounted on pivots 48 such that they are free to move as a unit.

Electrical contacts 50, 52, carried at the free ends of the bimetallic elements 40, 42, respectively, cooperate with adjustable stationary contacts 54, 56 respectively, which are connected to the electrical circuit by leads 58, 60. Initially those contacts are adjusted with one set of contacts closed to a suitable clearance at the other set of contacts, such as 0.010 inch.

This heat sensor has its bimetallic leaf elements directly disposed in the flow of air through the fire detector casing. When the detector elements 40, 42 are exposed to a sudden blast of hot air the bimetallic element 42 having the smaller mass will move more rapidly than the compensator element 40 and will close the circuit between the contacts 52, 56 to energize lines 58, 60'. However, in response to a gradual rise in temperature the compensator leaf 40 will move in response to the increased temperature at a rate related to, but somewhat slower than, the movement of the actuator leaf 42 and pivots the block 46 so that at a temperature between 15 F. and 185 F. (depending on the initial setting of the contacts) the heat sensor circuit will be closed to provide an alarm signal.

With reference to the electric circuit shown in FIG. 3, the particle or smoke sensor cell 30 (type 408) and the heat sensor 18 are connected in parallel to the input circuit of the starter electrode 62 of a cold cathode thyratron 64 (type 5823). Resistors 66 and 68 and capacitor 70 provide an input coupling network of the signals to the starter electrode 62. When the starter electrode 62 is energized the thyratron will conduct current via the anode 72 and cathode 74, energizing relay coil 76 of the differential relay 78. Also connected in the anode circuit of the thyratron is a reset switch 80, a rectifier 82, a resistor 84 and a capacitor 86.

A second coil associated with the differential relay 88 is connected in series between the lamp 34, the heater element 20 and a rectifier 90. A flux conducting element 92, magnetically coupled to both the relay coils 76 and 88, controls the position of an armature 94 which operates a set of normally closed contacts 96 to control the energization of alarm 98.

When the fire detector is supplied with power and, provided the lamp 34, resistor 20, relay coil 88 and rectifier 90 are all in working order, flux is induced in the element 92 to move the armature 94 and open the contacts 96, thus de-energizing the alarm unit 98. Should any of these series connected elements be defective so that the circuit cannot be completed the alarm circuit will be energized indicating that a failure has occurred.

Until a smoke condition is detected by the cell 30 or a temperature condition is detected by heat sensor 18, no current flows in coil 76 and the relay contacts 96 remain open under the influence of the flux from coil 88. When thyratron 64 becomes conductive, however, current flows in coil 76, producing a flux that cancels the effect of the flux from coil 88 so that the armature 94 closes contacts 96 energizing the alarm unit 98. The flux produced by the two coils are proportioned so that they After the thyratron is fired the alarm circuit will continue to be energized even though the cause of the alarm signal from the sensor (or sensors) may terminate since the thyratron is connected to a DO. source and extinguishes itself only when that source is removed. The anode circuit may be opened by the reset button 80 which de-energizes the thyratron and allows the alarm contacts 96 to open under the influence of coil 88.

Thus it will be seen that the invention provides a compact, reliable fire detention unit suitable for home or factory fire detection installations, which employ a plurality of different fire condition sensors. In the disclosed embodiment smoke detection means is provided that operates on the principle of reflected light and will respond to a light obscurity condition of approximately 10%, while heat sensor means is provided that responds either to a temperature value or to a rate of temperature change,

either response being adjustable as a function of the type of fire environment in which the detector is placed, for example. The circuitry positively responds when either a temperature or a smoke condition is detected and main tains an alarm condition independently of the sensor condition after initial detection of such a fire condition until the circuit is manually reset. The circuit components provide a reliable system employing only a single active element (a thyratron) which is energized only upon detection of a fire condition to sound the alarm. The circuitry is substantially maintenance free except for the need to periodically replace the light source and the circuitry is arranged to automatically provide an alarm when that element fails.

While a preferred embodiment of the invention has been shown and described, modifications thereof will be obvious to those skilled in the art and therefore it is not intended that the invention be limited to the disclosed embodiment or to details thereof and departures may be made therefrom within the spirit and scope of the in vention as defined in the claims.

I claim:

1. A signaling apparatus comprising a casing, having an entrance aperture and an exit aperture,

said casing defining a passageway between said entrance aperture and said exit aperture, allowing a substantially unrestricted flow of air through the casing,

a particle sensor including a light radiation sensor disposed for scanning the air flow through said passagey,

and a light radiation source having a beam directed generally perpendicular to the scanning direction of said radiation sensor and across the scanned area,

a heat sensor disposed adjacent said entrance aperture,

a gain producing element,

a two coil differential relay including contacts controlled by said relay connected in circuit with an alarm,

means connecting one coil of said differential relay in electric series circuit with said gain producing element and the other coil of said differential relay in electric series circuit with said radiation source,

first electric circuit means connecting said radiation sensor and said heat sensor in parallel, second electric circuit means connecting said first electric circuit means to said gain producing element to control the operation of said gain producing element,

said differential relay operating said relay control contacts to produce an alarm signal in response to operation of said gain producing element or failure of said radiation source.

70 2. The apparatus as claimed in claim 1 wherein said heat sensor is a bimetallic structure having a pair of himetallic elements positioned immediately above said entrance aperture,

said pair of bimetallic elements being mounted for pivoting movement as a unit,

one of said bimetallic elements being an actuator memphotocell disposed for scanning the air flow through her and the other of said bimetallic elements being said passageway, a compensator member of substantially greater mass and a light source having a focused beam directed than said actuator member. generally perpendicular to the scanning direction of 3. A signaling apparatus comprising a casing having said photocell and across the area scanned by said an entrance aperture, an exit aperture and a passageway photocell so that light reflected from particles in the between said entrance and exit apertures which allows air flow through said passageway may be detected a substantially unrestricted flow of air through the casing, by said photocell,

a particle sensor disposed in said casing including a photocell disposed for scanning the air flow through a heat sensor including a pair of bimetallic elements mounted in parallel relation for pivoting movement said passageway, 10 as a unit immediately adjacent said entrance aperture and a light source having a focused beam directed and P 0f fixed Contacts,

generally perpendicular to the scanning direction f each bimetallic element carrying an electrical contact said photocell and across the area scanned by said adapted to cooperate with the corresponding fixed photocell so that light reflected from particles in the Contact: air flow through said passageway may b d d means for producing air flow through said passageway by said photocell past said heat sensor and said particle sensor, a heat sensor including a bimetallic element mounted a thyratmn tube having an anode element and a immediately adjacent said entrance aperture and a element fixed Contact, a differential relay having a first coil connected in elecsaid bimetallic element Carrying an electrical Contact tric circuit with said anode element of said thyratron adapted to cooperate with said fixed contact, tube means for producing air flow through said passageway a second coil connected in series circuit with said light past said heat sensor and said particle sensor, source and Said means for Producing air an electronic switching element having an input circuit and a set f reiay Contacts and an Output circuit an alarm circuit connected to said set of relay contacts, a differential relay having a first coil connected in elec said second coil of said differential relay being connected tric circuit with the output circuit of said electronic to produce Via Said Set Of l y C n'tacts, a signal in switching element, sald alarm circuit in response to failure of said light a second coil connected in series circuit with said light source sald means for producing air source, and electric connector means for connecting said photoand a set of relay contacts cell and said pair of fixed contacts in parallel to the an alarm circuit connected to said set of relay contacts, i Control element 9 Said thyratmn tube to Operate said second coil of said differential relay being consaid thyratrpn m .isponse to fire condition nected to produce via said set of relay contacts, a 3 sensed by elther Said P or said heat sen- :signal in said alarm circuit in response to failure of 9 and.pmduce a slgnai sald first coil of said said light source differential relay for providing a signal in said alarm and electric connector means for connecting said p-ho-toclrcult Vla said set of relay Contacts" cell and said fixed contact in parallel to the said R input circuit of said electronic switching element to eferences Cited by the Exammer operate said electronic switching element in response UNITED STATES PATENTS to a fire condition sensed by either aid par icl p- 2,033,466 3/1936 Gran-t 88-14 sor or aid heat sensor and produce a signal 1n s l 2,119,326 5/1938 Grant 340 237 first co il of sa1d differential relay for p o g a 2,299,529 10/1942 Crampton 88-44 signal in said alarm circuit via said set of relay 2 537 023 1 1951 c h 1 34 237 contacts. 2,682,613 6/1954 Uhl 88-14 4. A slgnalll'lg apparatus O PUSI g a ca ing d fimng 2,769,879 11/1956 Steiner 340 227 an entrance aperture, an exlt aperture and a p'as g y 2,832,915 4/1958 McCoy 315-471 between said entrance and exlt apert res whi h a ow 2,982,950 5/1961 Boyle 340-'237 a substantially unrestricted flow of air through the casmg,

a particle sensor disposed in said casing including a NEIL C. READ, Primary Examiner. 

1. A SIGNALING APPARATUS COMPRISING A CASING, HAVING AN ENTRANCE APERTURE AND AN EXIT APERTTURE, SAID CASING DEFINING A PASSAGEWAY BETWEEN SAID ENTRANCE APERTURE AND SAID EXIT APERTURE, ALLOWING A SUBSTANTIALLY UNRESTRICTED FLOW OF AIR THROUGH THE CASING, A PARTICLE SENSOR INCLUDING A LIGHT RADIATION SENSOR DISPOSED FOR SCANNING THE AIR FLOW THROUGH SAID PASSAGEWAY, AND A LIGHT RADIATION SOURCE HAVING A BEAM DIRECTED GENERALLY PERPENDICULAR TO THE SCANNING DIRECTION OF SAID RADIATION SENSOR AND ACROSS THE SCANNED AREA, A HEAT SENSOR DISPOSED ADJACENT SAID ENTRANCE APERTURE, A GAIN PRODUCING ELEMENT, A TWO COIL DIFFERENTIAL RELAY INCLUDING CONTACTS CONTROLLED BY SAID RELAY CONNECTED IN CIRCUIT WITH AN ALARM, MEANS CONNECTING ONE COIL OF SAID DIFFERENTIAL RELAY IN ELECTRIC SERIES CIRCUIT WITH SAID GAIN PRODUCING ELEMENT AND THE OTHER COIL OF SAID DIFFERENTIAL RELAY IN ELECTRIC SERIES CIRCUIT WITH SAID RADIATION SOURCE, FIRST ELECTRIC CIRCUIT MEANS CONNECTING SAID RADIATION SENSOR AND SAID HEAT SENSOR IN PARALLEL, SECOND ELECTRIC CIRCUIT MEANS CONNECTING SAID FIRST ELECTRIC CIRCUIT MEANS TO SAID GAIN PRODUCING ELEMENT TO CONTROL THE OPERATION OF SAID GAIN PRODUCING ELEMENT, SAID DIFFERENTIAL RELAY OPERATING SAID RELAY CONTROL CONTACTS TO PRODUCE AN ALARM SIGNAL IN RESPONSE TO OPERATION OF SAID GRAIN PRODUCING ELEMENT OR FAILURE OF SAID RADIATION SOURCE. 